A recent study by the U.S. International Trade Commission indicates that counterfeiting of name brand goods is presently costing American businesses up to 8 billion dollars in lost sales annually. In addition, the counterfeiting is effectively costing the work force some 131,000 jobs per year. Still more startling is the fact that the counterfeiting menace is increasing. The growth of counterfeiting, however, should be easy to understand when the huge profits obtainable by the counterfeiter on the sale of low quality bonus goods at name brand prices are considered.
In order to combat the counterfeiting problem, technologies have developed for placing an identifiable marker or tag on the name brand goods. Of course, the markers themselves must be made very difficult to counterfeit in order to be effective. Typically, the marking system is designed so that at the least the cost of breaking the code and reproducing the marker or tag is prohibitive to the counterfeiter. However, on the other hand, the markers and the identifying system must be produced at a relatively low cost so as to make the concept economically feasible to the brand name manufacturer seeking bq protect its product.
An example of a tagging or marking system is found in U.S application of Anderson et al, patent Ser. No. 373,061 filed Apr. 29, 1982 now U.S. Pat. No. 4,510,489, entitled Survillance Systems Having Magneto Mechanical Marker. The marker includes an amorphous ferromagnetic strip or ribbon target adapted to generate a specific identifiable signal in response to interrogation with an applied magnetic field. The resonance frequency of the response signal is known since it is a function of the amorphous metal composition and the length of the ribbon.
As shown in the Anderson et al application, markers of this kind are presently used in theft detection systems. A transmitting apparatus including a drive coil is situated on one side of a passage leading to an exit from the premises. A receiving coil is positioned at the opposite side of the passage. The drive coil produces an interrogation signal that energizes the target ribbon. Once energized, the target ribbon produces an identifiable response signal that is received by the receiving coil. The presence of the response signal indicates that the target has not been properly deactivated or removed from the marked article by the cashier.
In such a theft detection system, the drive and receive coils of the antenna are spaced apart the width of the passageway, possibly as much as six feet. Thus, the interrogation zone defined between the drive and receive coils is quite large. The drive coil must, therefore, be adapted to apply a wide, strong magnetic interrogation field in order to energize and detect targets in the passageway leading to the exit.
If targets of this type are to be adapted for product verification, it is desirable to have a large number of different marker codes to prevent or discourage counterfeiting of the markers. One way we have discovered to do this is through the use of one or more amorphous ribbons of different length in each marker; each ribbon resonating in response to the interrogation field at a different identifiable frequency. However, where a wide range drive coil is used to interrogate the targets in the prior art, only the presence of the different frequency ribbons (in no particular sequence) may be determined. We have found there is n previously-known way to determine the order or sequence of the ribbons in the marker.
Thus, a need is identified for a short range, narrow interrogation zone antenna allowing for efficient scanning and detection of identification markers. Further, an integral, dual purpose antenna is desired capable of detecting the order or sequence of different frequency signal producing ribbon targets in a marker. Such an antenna allows for a greater number of marker codes as the multiple ribbons may be lined up side-by-side and read in sequence. Where original manufactured articles are properly marked, any variation in the frequencies present, or in the order of the frequencies, indicates that the marked article is a counterfeit. Such an antenna also has ready application to other security devices where an increased number of codes is desirable, such as in card reading devices, remote control locks, article surveillance devices, and personal identification systems.